<template>
  <div class="spec-preview">
    <img :src="imgObj.imgUrl" />
    <div class="event" @mousemove="handler"></div>
    <div class="big">
      <img :src="imgObj.imgUrl" ref="big"/>
    </div>
    <!-- 遮罩层  这里获取遮罩层的DOM,我们以后都用ref来绑定-->
    <div class="mask" ref="mask"></div>
  </div>
</template>

<script>
  export default {
    name: "Zoom",
    props:['skuImageList'], //接收父组件Detail传过来的数据
    data() {
      return {
        currentIndex: 0
      }
    },
    computed: {
      imgObj() {
        return this.skuImageList[this.currentIndex]||{} 
      }
    },
    mounted () {
      // console.log(this.skuImageList);//测试数据
      //全局事件总线,获取兄弟组件传递过来的索引值
      this.$bus.$on('getIndex',(index)=>{
        // console.log(index)
        // 修改当前响应式数据
        this.currentIndex = index
      })
    },
    methods: {
      handler(event) {
        // console.log(123)
        let mask = this.$refs.mask //获取遮罩层这个元素
        let big = this.$refs.big //获取大图的这个元素
        let left = event.offsetX - mask.offsetWidth/2  //offsetWidth/2遮罩层宽度的一半,offsetX是从遮罩层的中心开始算的
        let top = event.offsetY - mask.offsetHeight/2 //距离顶部的距离
        //约束范围
        if(left <= 0) left = 0  //约束最小的距离左边的距离不能小于0
        if(left >=mask.offsetWidth) left = mask.offsetWidth  //约束最大的距离left不能大于一个遮罩层的宽度,因为刚好两个遮罩层等于容器的宽度
        if(top <=0) top = 0 
        if(top >=mask.offsetHeight) top = mask.offsetHeight
        //修改元素的left|top属性值
        mask.style.left = left + 'px'
        mask.style.top = top + 'px'
        big.style.left = -2 * left + 'px'
        big.style.top = -2 * top + 'px'
      }
    },
  }
</script>

<style lang="less">
  .spec-preview {
    position: relative;
    width: 400px;
    height: 400px;
    border: 1px solid #ccc;

    img {
      width: 100%;
      height: 100%;
    }

    .event {
      width: 100%;
      height: 100%;
      position: absolute;
      top: 0;
      left: 0;
      z-index: 998;
    }

    .mask {
      width: 50%;
      height: 50%;
      background-color: rgba(0, 255, 0, 0.3);
      position: absolute;
      left: 0;
      top: 0;
      display: none;
    }

    .big {
      width: 100%;
      height: 100%;
      position: absolute;
      top: -1px;
      left: 100%;
      border: 1px solid #aaa;
      overflow: hidden;
      z-index: 998;
      display: none;
      background: white;

      img {
        width: 200%;
        max-width: 200%;
        height: 200%;
        position: absolute;
        left: 0;
        top: 0;
      }
    }

    .event:hover~.mask,
    .event:hover~.big {
      display: block;
    }
  }
</style>